The DFT Circular Convolution Property

Identify the operation in the time domain that corresponds to multiplication of $N$ DFT coefficients $H[k]X[k]$

If $x[n]$ is length 15 and $h[n]$ is length 20, what is the length of the linear convolution of $x[n]$ with $h[n]$?

Suppose $x[n]$ is length $M$ and $h[n]$ is length $L$. You compute the $N$ point circular convolution of $x[n]$ and $h[n]$ where $N>M, N>L$. How big should $N$ be for the circular convolution to be equal to the linear convolution of $x[n]$ and $h[n]$?